1. Field of the Invention
The invention relates to a ceramic electronic component, a method of manufacturing the same, and a collective component and, more particularly, to a ceramic electronic component in which an external conductor, such as an external terminal electrode, is formed on a principal surface and which is obtained by breaking a collective component along a predetermined break line, a method of manufacturing the same, and a collective component from which a plurality of ceramic electronic components may be obtained by dividing the collective component.
2. Description of the Related Art
In recent years, a large number of monolithic ceramic electronic components, typically, monolithic ceramic capacitors, are used in electronic apparatuses, such as cellular phones and personal computers. Generally, the monolithic ceramic electronic component includes a rectangular parallelepiped ceramic element assembly and a pair of external terminal electrodes formed on an outer surface of the ceramic element assembly. The external terminal electrodes are mostly formed in such a manner that conductive paste is applied to end portions of the ceramic element assembly by an immersion method and is baked. In this case, each external terminal electrode is formed to extend over five surfaces in total with one end surface of the ceramic element assembly as a center.
In recent years, there had been an increase in the demand for electronic components for specialized applications, and the like, and the shape and arrangement of the external terminal electrodes of the ceramic electronic component have become progressively diversified. For example, Japanese Unexamined Patent Application Publication No. 2006-216622 and Japanese Unexamined Patent Application Publication No. 2006-339337 suggest a type in which external terminal electrodes are formed on one surface or two opposite surfaces of the ceramic element assembly.
In this way, it is possible to form the external terminal electrodes by methods other than the immersion method when the external terminal electrodes are formed on one surface or two opposite surfaces of the ceramic element assembly. For example, there is a method where a conductive paste film for external terminal electrodes is printed on a principal surface of a collective component that constitutes a plurality of ceramic element assemblies for a plurality of ceramic electronic components and is baked, and then the collective component is divided to obtain the ceramic element assemblies for individual ceramic electronic components, which is, for example, described in Japanese Unexamined Patent Application Publication No. 9-260187 (particularly, at paragraph [0003]).
Because the collective component to be divided is formed of sintered hard ceramics, if a cutter, such as a dicer, is used to divide the collective component, there is a possibility that a crack or a chip may occur in the ceramic element assembly of each ceramic electronic component. To solve the above problem, Japanese Unexamined Patent Application Publication No. 9-260187 suggests that the unfired collective component is press-cut by a plate-like cutting blade. However, there is a problem that in this method, raw chips tend to stick one another after cutting.
Another conceivable method is a break method that is often used in manufacturing a ceramic multilayer board, or the like. In the break method, a break groove is formed in an unfired collective component, and, after firing, a collective component is divided along the break groove. Thus, the problem when a dicer or a plate-like cutting blade is used as described above is avoided. In addition, it is excellent in production efficiency as well because a plating process or a measurement process may be performed on the collective component.
Various break methods have been suggested. Among others, the break method described in Japanese Unexamined Patent Application Publication No. 2003-273272 is attractive. According to a technique described in Japanese Unexamined Patent Application Publication No. 2003-273272, by forming discontinuous linear break grooves, it is possible to prevent the occurrence of an undesirable crack in a collective component when subsequently handling the collective component in other processes.
On the other hand, it has been suggested in recent years to bury a ceramic electronic component inside the multilayer wiring board in order to miniaturize a multilayer wiring board. For example, Japanese Unexamined Patent Application Publication No. 2005-064446 describes a method of manufacturing a laminating module, which includes processes in which, when a ceramic electronic component is buried inside a board, the ceramic electronic component is accommodated in a core board so that an external terminal electrode formed on a principal surface of the ceramic electronic component is, for example, positioned to face upward, an insulating layer is formed so as to cover the core board and the ceramic electronic component, the insulating layer is punctured by a laser beam to form a via hole that reaches the surface of the external terminal electrode, and then the via hole is filled with a conductor to electrically connect a wiring circuit with the external terminal electrode.
In the above burial, accurate laser beam irradiation is required. This is because there is a possibility that the characteristics of the ceramic electronic component are changed if a laser beam is not carefully irradiated on the ceramic element assembly.
Thus, the area of the external terminal electrode of the buried ceramic electronic component is desirably as large as possible. For example, it is necessary to design external terminal electrodes 2 and 3 in the monolithic ceramic electronic component of a type described in Japanese Unexamined Patent Application Publication No. 2006-216622 and Japanese Unexamined Patent Application Publication No. 2006-339337, as shown in FIG. 17, so as to increase the areas thereof as much as possible with leaving only a necessary gap 1.
However, when the method of breaking along a predetermined break line in which the break grooves are formed by discontinuous perforations is used to manufacture the ceramic electronic components in which a plurality of external terminal electrodes having narrow gaps in between them are formed as described above, it is found that a “break defect” tends to occur. The “break defect” is such that a portion of a side surface of a ceramic element assembly, formed by the breaking, has a portion which is not broken properly, and, therefore, a protrusion (dent at the opposite side) is formed at the side surface or a crack or a chip occurs in the ceramic element assembly starting from the gap portion.
When discontinuous equal-sized recesses for leading a break are formed at an equal pitch, as described in Japanese Unexamined Patent Application Publication No. 2003-273272, it is highly likely that no recess which can lead the break is formed at a narrow gap portion and two adjacent recesses for leading the break are arranged so as to place the gap portion in between them. In this case, it is easy to concentrate tensile stress between adjacent recesses for leading a break in external terminal electrode forming portions that occupy the majority of the principal surface, whereas it is difficult to concentrate tensile stress on a gap portion that has a narrow area and that is located at a level slightly lower than the external terminal electrode forming portion. For this reason, it is predictable that a “break defect” tends to occur starting from the gap portion.